Joints and connections – Rod end to transverse side of member – Including saddle
Reexamination Certificate
1999-04-06
2001-05-22
Browne, Lynne H. (Department: 3629)
Joints and connections
Rod end to transverse side of member
Including saddle
C403S239000, C403S230000, C403S248000, C403S059000, C403S061000, C403S112000, C403S113000, C403S116000, C403S117000, C606S064000, C606S075000, C411S353000, C411S352000, C411S354000
Reexamination Certificate
active
06234705
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for spinal fixation, and in particular to a transconnector for coupling spinal rods, plates, or other elongate members.
BACKGROUND OF THE INVENTION
It is often necessary to surgically treat spinal disorders such as scoliosis. Numerous systems for use in spinal correction and fixation have been disclosed. These systems usually include a pair of elongate members, typically either rods or plates, placed on opposite sides of the vertebral column. Each rod is attached to the spine with various attachment devices. These attachment devices include pedicle screws, plates, spinous process hooks, sublaminar hooks, and pedicle hooks.
It is also well known that the strength and stability of the dual rod assembly can be increased by coupling the two rods with a cross-brace or transconnector which extends substantially horizontal to the longitudinal axes of the rods across the spine. The simplest situation in which a transconnector could be used occurs when the two rods are geometrically aligned. Specifically, the two rods are parallel to each other, i.e. there is no rod convergence or divergence in the medial-lateral direction; the two rods have the same orientation with respect to the coronal plane in the anterior-posterior direction, i.e. the rods are coplanar from a lateral view; and the two rods are located a fixed, predetermined distance from each other.
Due to a wide variety of factors, the two rods are rarely geometrically aligned in clinical situations. There are several ways to address the variations from geometrical alignment. First, one or both of the rods can be bent to accommodate the transconnector. However, any bending in either of the rods can adversely affect the fixation to the spine and comprise clinical outcome. Furthermore, the bending can also adversely affect the mechanical properties of the rods. The transconnector can also be bent so that the disturbance to the rod positioning is minimized. As was the case with bending of the rods, the mechanical properties of the transconnector could be compromised.
Transconnectors with some adjustability have been designed to adapt for variations from geometrical alignment. However, most are multi-piece systems that can be difficult to assemble and use in the surgical environment. Even those that are one-piece designs do not allow for adjustments to compensate for all three modes in which there may be variation from geometrical alignment: convergence or divergence, non-coplanar rods, and variability in rod separation distances.
Thus, there exists a need for an improved transconnector for coupling spinal rods.
SUMMARY OF THE INVENTION
The present invention relates to a transconnector for coupling first and second elongate spinal fixation elements that have different orientations with respect to a plane. The transconnector includes a male member, a female member and a locking member and can be made of any suitable material such as titanium, a titanium alloy, or stainless steel. The male member comprises a body with lateral and medial ends, a linking element associated with the lateral end and being configured and dimensioned to receive one of the fixation elements, and a projection extending from the medial end. The female member comprises a body with lateral and medial ends, a linking element associated with the lateral end and being configured and dimensioned to receive one of the fixation elements, and a cavity with an opening on the medial end which is configured and dimensioned to receive a portion of the male member projection. The locking member adjustably and rotatably secures the male member projection portion in the cavity in order to accommodate different orientations and separation distances between the first and second fixation elements.
In a preferred embodiment, the male member projection is substantially cylindrical and has a pin extending perpendicularly from its longitudinal axis. The pin is slidable in a slot located in a wall of the female member cavity for adjusting the portion of the projection received in the cavity. The slot has a width which is wider than the diameter of the pin so that the projection can rotate in the cavity. In order to further increase the degree of rotation, the side edges of the slot may angle outwardly.
Preferably, the locking member comprises a threaded hole in the body of the female member and a set screw threadably received in the threaded hole. The set screw has a first end for receiving a tool to turn the set screw and a second end contactable with the projection for pressing the projection against the cavity.
The male member body may comprise a link terminal having a lateral end with the male member linking element, an intermediate link having a medial end with the projection of the male member and a lateral end engaging the medial end of the link terminal, and a locking element for securing the link terminal to the intermediate link. Preferably, the medial end of the link terminal includes a first textured surface and the lateral end of the intermediate link includes a second textured surface mating with the first textured surface. The first textured surface is rotatable with respect to the second textured surface for accommodating convergence or divergence between the first and second rods. An example of suitable first and second textured surfaces includes a star-grind pattern.
The locking element preferably comprises a first hole through the medial end of the link terminal, a second hole through the lateral end of the intermediate link aligned with the first hole, and a cap screw insertable in the first and second holes. The cap screw may have a second end with a retaining ring for preventing removal of the cap screw from the first and second holes. The retaining ring may include a resilient member which flexes inward upon insertion of the cap screw through the first and second holes and flexes outward once the resilient member is past a collar in the second hole. Preferably, the resilient member includes an end of the cap screw with a lip and a plurality of slits.
If rods are used for the elongate fixation elements, then the male member linking element preferably comprises a hook and the female member linking element preferably comprises a hook. The lateral ends of the male and female members each may include a threaded hole and a clamping screw threadably received in the respective threaded hole for securing the fixation elements to the respective hook. The fixation elements are preferably clamped between a conical second body portion of the respective clamping screw and a region near the tip portion of the respective hook when the fixation elements are secured to the transconnector.
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Browne Lynne H.
Garcia Ernesto
Pennie & Edmonds LLP
Synthes (USA)
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